Experts agree investors are at their worst when markets become volatile—and volatile is exactly the word to describe the market this year.

The S&P 500 swooned almost 5% in January, was flat in February and jumped over 6.5% in March, all after recovering last year’s 8% drop from August to September, the Wall Street Journal reports. Crazy markets like this often make investors irrational and lead them to trade in damaging ways, according to Morningstar’s “investor returns” metric.

Investors selling and buying at the wrong moments, especially when things get a bit panicky, has led to their missing an average of almost 1.8 percentage points of a fund’s annualized total returns over the last decade. While there is no sure way to prevent poor trading, experts urge investors to stick to a prearranged investment plan, and not to get scared when things drop unless it hits the exposure limits of their plan. [WSJ]